Read character with custom 128 bit UUID

RE: Read character with custom 128 bit UUID

Kenneth — Thu, 02 Jun 2022 17:06:03 GMT

[quote user="KonstantinK"]I don't know why I am not getting the event after sd_ble_gattc_char_value_by_uuid_read() call..[/quote]

Me neither, I suggest you try to continue to debug, and just try and fail a bit, e.g. try with another peer for testing, try to add some delays between calling api calls etc.

Kenneth

RE: Read character with custom 128 bit UUID

KonstantinK — Thu, 02 Jun 2022 12:08:55 GMT

I implemented the error check afterwards and there is no error returned by either of the API calls. I also implemented the function for discovering the characteristics and there are all characteristics returned at the BLE_GATTC_EVT_CHAR_DISC_RSP event with type 0x02 (which is the same which is returned at the sd_ble_gattc_char_value_by_uuid_read() call). This means the custom base uuid is assigned correctly, or am I wrong?

I don't know why I am not getting the event after sd_ble_gattc_char_value_by_uuid_read() call..

RE: Read character with custom 128 bit UUID

Kenneth — Thu, 02 Jun 2022 11:53:51 GMT

[quote user="KonstantinK"]Do you now why it returns NRF_SUCCESS but I doesn't even get the BLE_GATTC_EVT_CHAR_VAL_BY_UUID_READ_RSP event?[/quote]

No, so please double check that neither api calls return an error, I can at least from the code snippet you shared see that you are not checking err_code for neither of the api calls.

Kenneth

RE: Read character with custom 128 bit UUID

KonstantinK — Thu, 02 Jun 2022 11:39:15 GMT

Yes, I am checking at sd_ble_uuid_vs_add and sd_ble_gattc_char_value_by_uuid_read and it always return NRF_SUCCESS.

The strange thing is that I am not getting the event when I use the UUID.type from sd_ble_uuid_vs_add(). Only if I set it to 0x01.

Do you now why it returns NRF_SUCCESS but I doesn't even get the BLE_GATTC_EVT_CHAR_VAL_BY_UUID_READ_RSP event?

RE: Read character with custom 128 bit UUID

Kenneth — Thu, 02 Jun 2022 11:31:49 GMT

Are you checking the err_code for each call?

Kenneth

RE: Read character with custom 128 bit UUID

KonstantinK — Thu, 02 Jun 2022 10:21:39 GMT

Hello, thanks for the reply. I have edited my code and it looks like this currently:

read_char_uuid.uuid = 0x30b9;

ble_uuid128_t const base_read_char_uuid =
{
		{
				0x96, 0x4B, 0x56, 0x94, 0xC0, 0x6D, 0x73, 0x9A,
				0x91, 0x4C, 0xCC, 0x28, 0xb9, 0x30, 0x02, 0x47
		}
};


//assign custom uuid to ble stack
err_code = sd_ble_uuid_vs_add(&base_read_char_uuid, &read_char_uuid.type);

ble_gattc_handle_range_t read_handle_range = {0x0001, 0xffff}; 

//call read function
err_code = sd_ble_gattc_char_value_by_uuid_read(m_conn_handle, &read_char_uuid, &read_handle_range);

With this implementation I don't even get a BLE_GATTC_EVT_CHAR_VAL_BY_UUID_READ_RSP event. So I can't even check if the attribute is found or not.

If I change the read_char_uuid.type = 0x01, I get the event but obviously no correct response data. Since I don't even get an event with my read_char_uuid.type from sd_ble_uuid_vs_add(), do you think there is an issue with the base uuid or how should I provide it?

The UUID for this characteristics is displayed like this on the nrf Connect mobile app: 470230b9-28cc-4c91-9a73-6dc094564b96

Or should I call the sd_ble_gattc_char_value_by_uuid_read more often with new handle_range.start?

I tried the things from the posts you mentioned already...

Thanks for your help

EDIT: I got the event now and if I check the gattc_status like you mentioned I get the status BLE_GATT_STATUS_ATTERR_INVALID_HANDLE 0x0101.

Do you know where the problem might be or what does this mean?

RE: Read character with custom 128 bit UUID

Kenneth — Thu, 02 Jun 2022 09:52:03 GMT

Hello,

I suspect that if you check p_ble_evt->evt.gattc_evt.gatt_status on BLE_GATTC_EVT_CHAR_VAL_BY_UUID_READ_RSP event you can find that p_ble_evt->evt.gattc_evt.gatt_status is BLE_GATT_STATUS_ATTERR_ATTRIBUTE_NOT_FOUND.

I suspect that your UUID is not formatted correct, e.g. when calling sd_ble_gattc_char_value_by_uuid_read() you need to both have read_uuid.type from sd_ble_uuid_vs_add() and read_uuid.uuid = 0x30b9;

If still problems you need to look at the byte orders (e.g. MSB and LSB). Some possible useful threads:

https://devzone.nordicsemi.com/f/nordic-q-a/86291/read-value-from-several-characteristics-as-central-to-a-custom-service
https://devzone.nordicsemi.com/f/nordic-q-a/52251/read-added-custom-characteristic-value-from-peripheral/
https://devzone.nordicsemi.com/f/nordic-q-a/20924/sd_ble_gattc_char_value_by_uuid_read---again

Best regards,
Kenneth